Purple nutsedge is the predominant nutsedge species in Arizona cotton fields. It is common to find very high density patches (more than 1000 shoots m^-2) of purple nutsedge four weeks after planting. Nutsedges are highly competitive, perennial weeds that reproduce rapidly from tubers and rhizomes. These plant characteristics make purple nutsedge a superior competitor with cotton reducing seed cotton yield and quality. One factor that influences the competitive balance between weeds and crops is soil moisture. Since moisture stress shifts the competitive balance in favor of cotton by reducing the interspecific competition, then it may be possible to hinder purple nutsedge growth with a good water management strategy.